Members of both parties in the Senate had asked the Obama administration to let Congress weigh in first, but the deal instead was taken to the Security Council, of which the United States is a permanent member, on Monday. All 15 members voted to back the deal reached last week.

Maryland Sen. Ben Cardin, the Democrat who signed the letter to Obama, appeared on "Fox News Sunday" over the weekend reiterating his belief that the United Nations should not have had the first opportunity at the agreement.

"I think it is not consistent with Iranian Review Act, so that's why I joined (Tennessee Republican) Sen. (Bob) Corker and urged the president to reconsider and wait 'til after the 60-day period," Cardin said. "It doesn't take effect 'til 90 days after the U.N. acts."

The Obama White House chose the United Nations first, Limbaugh argued, because it would put pressure on waffling Democrats.

"This is to obviate and render needless and irrelevant the United States Congress," Limbaugh said. "'Cause what do you think those mealy mouths are gonna do once the U.N.'s passed it? I can't see a bunch of Democrat senators standing up."

Further, he said, Democrats will use the U.N. vote to pass the buck on responsibility.

"Since the U.N.'s voted on it, it gives members of Congress a chance to say, 'There's nothing we can do now. We're off the hook. We don't have to stand up and vote against it because the world has already approved it,'" he said. " And that's what it was designed for, and there's no other way to look at this other than as a direct assault on U.S. sovereignty."

The White House doesn't care whether the deal is approved by the Senate anyway, Limbaugh said, just as long as it is implemented.

Secretary of State John Kerry was asked on "Face the Nation" on Sunday whether a "no" vote in Congress would undermine the deal.

"No, not in the least," Kerry said. "They don't care over there whether it's a majority or minority or whatever it is, as long as the deal is implemented, and that's what we care about, that this deal be implemented."

Limbaugh was incredulous.

"You just heard John Kerry say the Iranians don't care whether Congress approves it or not, they just want it implemented," he said. "And it's the same with us. We'd like the Congress to like it, but they don't, big (raspberry) deal."